Fascinating conversations with Uncle Paul reveal the mysteries behind the dyeing and weaving of cloth, the lighting and heating of homes, the processing involved in bringing oil, coffee, tea, spices, and other foodstuffs to the table, and the power of water in all its manifestations. Excellent as follow-on to The Story Book of Science. Ages 11-14

387 pages

$14.95

RAIN

[340]

"W

HAT is needed to make the half-condensed vapor of
clouds finish condensing and turn to water, falling in
drops of rain? Very little: a slight cooling, a breath
of cold air from some less heated region.

"As soon as it is cooled the fine aqueous dust of the
clouds, similar to what we see rolling up in the form
of fog, collects in very small drops which fall of
their own weight.

"In passing through the dense mist below them these
droplets condense on their surface a little of the
vapor they meet with, so that they increase in size and
become drops capable of growing still larger, until the
very moment of their leaving the clouds. Finally they
fall to the ground after attaining a size proportioned
to the thickness of the cloud-layer through which they
have passed.

"That is rain—one day a fine shower which hardly
bends the blades of grass, another day a heavy downpour
in big drops that patter on the foliage and the tiled
roofs. That, I say, is rain which we all so eagerly
desire when the country is suffering from drought.

"It rains beneath the clouds that are converted into
water by being chilled; but elsewhere it does not
[341] rain, the sky is blue, and the sun shines. One can
often see this uneven distribution of a rainfall. Has
is not happened to you that, with the sky all blue
overhead, you have seen in the distance something like
a vast grayish curtain, vertically striped and reaching
from the sky to the earth? That is a cloud turning into
rain and pouring out its contents wherever it passes.
It may even have reached you, driven in your direction
by the wind. Then the blue sky has suddenly become
somber, and you are caught in a shower.

"Clouds may be likened to immense celestial
watering-pots that travel almost everywhere at the
caprice of the winds that drive them. Every region they
visit receives a shower; but any other, however near it
may be, receives nothing so long as it does not lie
under them. A rainfall may be local in extent and its
limits so sharply defined that a few steps in one
direction will expose you to a shower and a few steps
in the other place you where not a drop falls. But
local rains are not the only ones. There are
some—and they often occur—that embrace
enormous regions, several provinces at a time.

"While the rain is falling, as we may imagine it to
fall, let us consider for a moment the marvelous
journey accomplished by a single raindrop. Whence does
it come? From the clouds floating there above our
heads, perhaps one or two thousand meters high. It was
up there when the thunder burst; it was present at the
blinding flash of the lightning. But no sooner was it
formed than, by the force of its own weight, it fell
with dizzy speed from its lofty
posi- [342] tion. Behold it rebounding from a leaf and falling to
the ground, where it soaks into the soil and adds to
the moisture essential to the life of every plant. A
head of lettuce, perhaps, in drinking it, will gain
renewed vigor.

"It came from the clouds, and clouds are made of vapor
held in the atmosphere. This in turn results from the
evaporation of water, chiefly the water of the sea, by
the heat of the sun. But of what sea? Who can say? Who
could indicate precisely from what point of the broad
ocean's surface the sun drew the vapor that was one day
to form that drop? Was it from the blue waves of the
Mediterranean, the smiling sea to the south of France?
It is possible, if the cloud from which it fell was
driven so far by the south wind. Or was it from the
greenish waves of the ocean whose billows dash
furiously against the cliffs of Normandy and the reefs
of Brittany? Possibly, if the west wind drove hither
the cloud that was to let it fall.

"It is possible, again, that the raindrop came from a
far greater distance, perhaps from some gulf fringed
with cocoanut-trees whereon perch green parrots with
red tails; perhaps from some arm of the sea where the
whale suckles its young; perhaps from the other end of
the world. Yes, there are all these possibilities; and
then what a journey to come to us and water a head of
lettuce!

"This prodigious journey ended, is our drop of rain at
last to find rest in the plant it has watered? By no
means. Nothing remains at rest in this world, not even
a drop of water. Everything is in
[343] motion, everything is busy, everything is forever
beginning again the task already accomplished.

"The drop of water rises with the sap from the roots of
the plant, ascends through the stalk, and reaches the
leaves, where it evaporates. The heat of the sun
reduces to vapor what it had for a moment relinquished
to the earth as water. And so we have again the drop of
water high in the heavens and transformed to an
invisible state—once more given over to the
caprices of wind and storm, which will carry it no one
knows whither. One day or another it will become rain
again, and there is no reason why it should not, sooner
or later, water the cocoanut-tree from the neighborhood
of which we supposed it to start.

"These journeys being repeated unceasingly, sometimes
in one direction, sometimes in another, the raindrop
cannot fail some day to rejoin the sea whence it
originally came. All rain comes ultimately from the
sea, and to the sea all rain finally returns."

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